Radiation-curable coatings are currently being used in a wide variety of applications. One advantage of a radiation-curable coating is that it eliminates the need for conventional solvents. A second advantage is that radiation-curable coatings may be applied to virtually any type of substrate, including, e.g., glass, textile fabrics, leather, metal, paper, wood, and polymeric substrates.
Acrylate resin(s) comprising, for example, acrylate monomer(s), is commonly used in a radiation-curable coating layer. Examples of typical acrylate monomers may include both low and high molecular weight acrylates, for example, monoacrylates, diacrylates, and triacrylates, e.g., hexanediol diacrylate, isobomyl acrylate, diethylene glycol diacrylate, trimethylol propane triacrylate, and beta carboxy ethyl acrylate. However, polymerization of the acrylates via, for example, ultraviolet radiation, typically requires a photoinitiator.
The U.S. Food and Drug Administration prohibits the use of nearly all photoinitiators in food packaging materials because photoinitiators are capable of yielding hazardous products upon irradiation. Consequently, polyacrylate has typically been excluded from the list of materials used in food packaging applications, or any other application that benefits from the omission of photoinitiator or photoinitiator residue.
U.S. Pat. No. 4,070,500 to Leitner, et al. discloses radiation-curable vehicles, and compositions containing such vehicles, for use in inks, paints, coatings, or similar compositions, such vehicles being operative without the inclusion of photoinitiators. The '500 patent, however, is silent regarding a composition comprising vinyl acrylate.
U.S. Pat. No. 5,725,909 to Shaw, et al. discloses a thermoplastic container or packaging material coated with a crosslinked acrylate layer. The '909 patent, however, does not at all mention a composition comprising vinyl acrylate. The '909 patent, moreover, does not exclude photoinitiators from its compositions. In fact, the '909 patent states that a photoinitiator may be included in the acrylate layer in order to facilitate polymerization by ultraviolet radiation.